This invention relates to valves used to control fluid streams, especially overflow control valves for hot liquid sodium flow.
Coolant pumps associated with liquid sodium fast breeder reactors are located inside a pressure boundary tank. Due to leakage around the pump shaft seals, an upper section of the tank is filled with hot liquid sodium. Leakage into the upper pump tank is continuous during pump operation. A steady, safe liquid sodium level in the tank is maintained by an overflow control valve which, if set properly, allows sodium flow equal to sealleakage flow to return to the pump suction via an overflow line. The purpose of the overflow control valve is to adjustably orifice the overflow line such that a safe liquid level in the tank is achieved.
Location of the overflow control valve within the tank is desired since the valve stem seal may then be in a cover gas/sodium vapor region rather than under liquid.
The overflow control valve should be easily removable from the tank for maintenance and inspection, but the valve must maintain a good seal with the tank wall during operation despite pump induced vibrations in the valve and tank.
It is desired to provide an easily removable overflow control valve with a sealing mechanism responsive to vibrations between the valve and a tank wall or seat, suitable for high temperature applications.